1. Field of the Invention
The invention relates to a method and to structure for at least partially balancing axial thrust loads experienced by a rotor of an engine.
2. Description of Related Prior Art
Most engines include rotors or shafts that rotate about a centerline axis. In a turbine engine, one or more rotors can support compressor blades and turbine blades. The compressor blades can be components of a compressor section for compressing fluid such as air. The turbine blades can be components of a turbine section downstream of the compressor section for converting the energy associated with combustion gases into kinetic energy. The rotor or rotors supporting the compressor blades and the turbine blades rotate about a centerline axis. The compression of fluid in the compressor section can generate axial thrust loads on the rotor or rotors along the centerline axis. Similarly, the conversion of energy associated with the combustion gases in the turbine section can generate axial thrust loads on the rotor or rotors along the centerline axis. Several factors can affect the extent of axial thrust loads; examples of these factors include, and are not limited to, the compression ratio of fluid, the firing temperature of combustion gases, and the thrust generated by the turbine engine.
Axial thrust loads can be addressed with thrust bearings supporting the one or more rotors of the turbine engine. Turbine engine designs that incur relatively high axial thrust loads incorporate relatively large thrust bearings. A balance piston is another structure applied in turbine engines to counteract axial thrust loads. In a balance piston arrangement, compressed air from a compressor of the turbine engine is applied against a pressure face of some structure acting as the piston. The piston is engaged with the one or more rotors of the turbine engine. The fluid pressure acts on the effective area of the pressure face to counteract the engine thrust. The term “balance” is used in the art, but the force generated on the rotor through a balance piston may not actually balance the forces on acting on the rotor.